A 243 AI might help the 243 w/stretch, but a 6mm Rem might be the simplest way and great performer.
The 6mm/6.5x47 is a nice round as it is, I might try one if:
A) stamped out the box brass was made
B) bbl life was better than a 243
One must not overlook a 6mmBR, not as in a 'race' against other 6mms, but in balance the total of bbl life, accuracy, ballistics, etc. It's a great round and VERY simple to load, and load w/accuracy. It won't match the 47, but if I wanted that performance, I might just do a custom 243 or 243 AI, run Lapua brass, as I believe they are cheaper yet than the 47s.
I DO think a 6mm Creedmoor, if Hornady did a 6 version, would be a very good performer.
Before the 47, many wildcatters just did a 6/250 or 6/250AI, as the 22 and 6.5 versions. Brass quality I am not sure about, but I think Norma mfg. 22/250, and perhaps Lapua even does. They run similar capacities. Now guys are also doing various versions of the 6BR, which AI'd so about 150 or more OVER the parent case, yet throttle down to 2950 w/105-108s for best accuracy.
